gigastasioFeb 20

I've had this puzzle on my phone for years. Every few months I'd glance at it and try and solve it. Last night, as I was eating dinner, I finally figured out the answer!

https://sh.itjust.works/post/55641581

Show threadEnkrodFeb 20

Hah, took me nearly a minute.

Tap for spoiler

Add the digits on both sides. ? = 12

But I only got it so quickly because I enjoyed a similar puzzle once.

1
11
21
1211
111221
312211
…

continue the series.

Show threadpiecat

Whaaat?

Isn’t it right parent minus left parent equals the node you pick?

Alternately right parent minus child equals left parent.

Why does it work with digits as well? What math sorcery is this??

Feb 21 at 3:13amWeb
Show threadprime_number_314159Feb 21
21 minus 13 is unfortunately not 7… Unless I’ve misunderstood what you mean?